Preparation And Performance Characterization Of Polymer Fiber-Optic Fluorescent Sensing Materials

Poly (methyl methacrylate) optical fibers (POF) sensor is a kind of optical devices which is used for response of external stimulation by light signal transmission, thus finish the sense to environmental physics or chemical parameters. POF sensors have many advantages, such as their large core, ease of handling and connections, flexibility, visible wavelength operating range, high numerical aperture and low price light mass of test equipment. On the other hand, it is already known that POF sensor based on evanescent field and total internal reflection (TIR) is a hot spot in current research and application as the advantage of simple in structure, low cost, high sensitivity, rapid response, cross discrimination and distribution sensing. In addition, organic sensitive materials with fluorescent sensing performance have been very active in research field of optical sensors. Organic materials not only can improve the response speed and detection accuracy, but also can realize the miniaturization of the optical fiber sensor. In this dissertation, a series of organic fluorescent sensing materials and corresponding reactive monomers were synthesized, characterized and used to fabricate POF fluorescent sensor by thiol-ene click reaction. The contents of this dissertation are as follows:1. Perylene-3,4,9,10-tetracarboxylic potassium salt (PTK) was synthesized by hydrolysis reactions in alkaline conditions using perylene-3,4,9,10-tetra-carboxylic dianhydride. Photophysical properties in aqueous solution were characterized by UV/vis and fluorescence spectra. The results show PTK has no effect on the fluorescence intensity in D-lactulose solution with relative high refractive index. There, PTK solution with different refractive index has been used as a fluorescent medium to study the fluorescence excitation, optical coupling and waveguide behavior of U-bent POF probe. Compared to the straight POF probe, theoretical and experimental analysis results show U-bent POF probe provides better fluorescent sensitivity due to the more evanescent wave excitation.2. Two kinds of porphyrins with different chemical structure were synthesized, including one containing four reactive allyl groups in meso position (TAPP). The chemical structures were confirmed1H NMR and HRMS. The two porphyrins show distinguishing fluorescent quenching responsive properties (Ksv) for nitroaromatic compounds (NACs) characterized by fluorescence spectrum in solution. Under evanescent wave-initiation, a porous film (POSS-thiol cross-linking film, PTCF) was synthesized in situ on the side surface of the fiber by a thiol-ene "click" reaction of viny1-functionalized polyhedral oligomeric silsesquioxanes (POSS-V8), alkane dithiols and TAPP. When vinyl-functionalized porphyrin, containing four allyl substituents at the periphery, is added into precursors for the polymerization, fluorescence porphyrin monomer can be covalently bonded into the cross-linked network of PTCF. This "fastened" way reduces the aggregation-induced fluorescence self-quenching of porphyrin and enhances the physicochemical stability of the porous film on the surface of U-bent POF. Fluorescent signals, emission by porphyrin in the PTCF/U-bent POF probe, exhibit high fluorescence quenching toward trace TNT and DNT vapor. In addition, the rapid, in situ fabrication of PTCF can be controlled by fiber evanescent wave for U-bent POF and straight POF, mostly the film thickness with the designed size. Fluorescent response of analyte was influenced by the microstructure of PTCF, and the highest fluorescence quenching efficiency is observed for1,6-hexanedimercaptan-based film.3. The bay (center ring position of perylene core)-dibromo-substituted perylene-3,4,9,10-tetracarboxylic bisanhydride (1,6/1,7-DBPDI) was synthesized by bromination of3,4,9,10-perylenetetracarboxylic acid anhydride (PDI). When imidization with n-butylamine and then with simple Ullmann reaction in bay position, a series perylene bisimide (1,6/1,7-PBIs) dyes can be obtained. Two pure regioisomers with N-methyl-piperazine substitution in bay position,1,7-disubstituted PBI (1,7-DMPPBI) and1,6-disubstituted PBI (1,6-DMPPBI), were successfully separated by column chromatography. The differences in the chemical structure of these two regioisomers, characterized by1H NMR and HRMS, are instantiated at the signals of methylene protons next to the imide nitrogen and the signals of aromatic region. Simultaneously, the two regioisomers have a clear distinction:first is the large molar absorption coefficient of1,7-DMPPBI, second is the more sensitive fluorescent turn-on performance of1,7-DMPPBI to sensing2,4,6-trinitrophenol (PA) by photoinduced electron transfer (PET) mechanism, third is the obvious color change from green to blue when sensing PA, and the last is the high selective recognition for PA of1,7-DMPPBI in acetonitrile solution. Reactive monomer of1,7-DMPPBI (DMPPBIM) was synthesized by saponification and subsequent amidation with allylamine. By thiol-ene "click" reaction of triallyl isocyanurate (TAIC), alkane dithiols and DMPPBIM, a versatile fluorescence sensor based on PA imprinted microstructures photo-polymerized in the tip of coaxial polymer optical fiber (MIP-CYPOF) was successfully prepared. Compared to non-molecular imprinted type (NIP-CYPOF), this MIP-CYPOF shows a highly sensitivity, selectivity and recyclability to PA. In addition, MIP-CYPOF has used to build a remote keypad.4.1,7-Dibromo-substituted perylene bisimides (1,7-DBPBIs) have been directly obtained in yields of at least60%in regioisomerically pure form by treating the commonly used dibromoperylene-3,4,9,10-tetracarboxylic dianhydride (DBPDI) with2-(diethylamino)ethylamine or2-(dimethylamino)ethylamine and then separating the regioisomeric mixtures by conventional column chromatography and without recrystallization. The1,7-dibromo isomer obtained with2-(dimethylamino)ethylamine in such a convenient and efficient way was further used to prepare1,7-disubstituted perylene bisimide derivatives (1,7-PBIs) by saponification, amidation, and then bay-position substitution reactions (Ullmann reactions). The individual regioisomers were fully characterized by1H NMR spectroscopy and HRMS. Photophysical properties of1,7-DBPBIs and1,7-PBIs were characterized by UV/vis and fluorescence spectra. The results show different substituent groups in peri positin have the different influence on the proton chemical shift of1,7-DBPBIs. The signals of the protons located in the aromatic region and neighboring the imide nitrogen atom were utilized to confirm the chemical structures of the isomers. As an important reaction intermediate raw materials,1,7-DBPBIs can be used to synthesize1,7-DBPDIs by full saponification reaction, and thus the corresponding amidation products (1,7-PBIs) also present the typical splitting of proton chemical shift of1,7-isomer. In addition, substituentions in peri positin have little effect on absorption spectrum of1,7-DBPBIs and1,7-PBIs. But obvious redshift of absorption and fluorescence spectrum can be found as the introduction of nucleophilic substituent groups in bay position.5. The introduction of2-(diethylamino)ethylamine or2-(dimethylamino)ethylamine to peri position of1,7-PBIs, simultaneously, provide PET type molecules with fluorescent turn-on properties. The fluorescent test show highly sensitivity of2-(dimethylamino) ethylamine imidizated PBI. By Ullmann reaction at bay 1,7-position with allyl4-hydroxybenzoate, reactive monomer (PBIM) was synthesized and thus can be used for thiol-ene click reaction. The chemical structure of1,7-subsitution/centrosymmetry of PBIM was retained after reaction and characterized by1H NMR. Fluorescent response at mixture solution of CH3CN and water show fluorescent turn-on for PA, and also D-aspartic acid (D-Asp). The responsive mechanism is based on the acid and alkali complexe (PBIM/D-Asp) form as pKa-matching, and thus the complexe inhibit PET process from tertiary amine to perylene core. Finally, a MIP-CYPOF fluorescent sensor has been prepared by using TAIC, alkane dithiols and PBIM/D-Asp complex at the tip of fiber. Compared to the CYPOF without MIP (NIP-CYPOF), the use of a PBIM in the MIP is an advantage as it simplifies the detection strategy for non-fluorescent D-Asp, and also improves the sensitivity, selectivity and recyclability of POF fluorescent sensor to D-Asp.